Hydraulic motor with speed change device



Feb. 2%, 1968 G. 1.. GUlNOT HYDRAULIC MOTOR WITH SPEED CHANGE DEVICE 2 Sheets-Sheet 1 Filed May 28, 1965 //V VE/V roe Feb. 20, 1968 r e. GUINOT 3,369,457

HYDRAULIC MOTOR WITH SPEED CHANGE DEVICE Filed May 28, 1965 2 Sheets-Sheet 2 m L L 3,369,457 HYDRAUMC MGTUR WITH SPEED CHANGE DEVICE Gabriel L. Guinot, Le Plessis-Belleville, France, assignor to Societe Anonyrne Poclain, Le Plessis- Belleville, France, a society of France Filed May 28, 1965, Ser. No. 459,864 Claims priority, application France, June 3, 1964, 976,362 Claims. (Cl. 91-16) ABSTRACT OF THE DISCLGSURE A multi-cylinder hydraulic motor having selective cylinders disconnectable from the source of power fluid having an auxiliary system for continuously supplying low-pressure fluid to those cylinders that are disconnected to prevent undue vibrations and wear.

Numerous types of hydraulic motors are known which comprise at least one cylinder block supported on a driven shaft rotatably mounted in a casing. A number of radial cylinders, within which pistons operate, are provided in the cylinder block, said pistons being supported preferably by rollers on an undulating cam integral with the casing. The pistons are operated by means of an hydraulic fluid delivered by a pump which feeds the cylinders through inlet and outlet ports in a distributor which may be flat or cylindrical.

Variations in the operating characteristics of such motors, and particularly in their speed and torque are usually obtained, either by modifying the delivery of hydraulic fluid under pressure or by modifying the cylinder volume, that is to say by taking a predetermined number ofcylinders out of service. However, in the latter case difliculties arise due to the fact that the pistons in the cylinders which are not fed with fluid can no longer be constrained to follow the undulations of the cam. In particular, there is the risk that these pistons produce troublesome out-of-balance forces and eventually strike the cam With great force thereby causing deterioration of both of the cams and the rollers.

The object of the present invention is to provide an improved arrangement and method of operation which ensures continuity of movement of the pistons in the cylinders which are not supplied with fluid, such an arrangement being applicable to all hydraulic motors which have one or a number of cylinder blocks supported on the same shaft. Nevertheless, the invention can be used to the best advantage on motors in which the cylinders are divided into a number of groups, feeding of the cylinders being effected either by a single conduit having obturators associated with each cylinder, or conversely by separate conduits associated with each group of cylinders.

According to one feature of the invention, connections are made between those cylinders which are not fed with fluid, in such a manner that their chambers which are connected provide with the connecting passages, a closed substantially fluid tight system independent of the hydraulic fluid supply circuit. In a great many cases, a sufficient number of structural parameters of the motor are made use of (number of cylinders, piston strokes, number of undulations in the cam and the shape of these etc.) for the sum of the volumes of the cylinders not fed with fluid to be constant, whatever the angular position of the cylinder block may be. Thus, the replenishing of certain chambers compensates exactly for the draining of others in such a Way that the pistons remain permanently in contact with the cam.

States Patent O However, in certain other cases, it will not be possible to satisfy the conditions just explained. Nevertheless, to preserve the advantages of the arrangement according to the invention, the enclosed system constituted by the assembly of cylinders which are not fed with fluid, will be connected to a source of fluid under pressure, for example to an accumulator, the pressure of which will still be below that of the fluid supply circuit of the motor. Thus, a replenishing and partial draining (called hereafter stuffing) of the enclosed system of cylinders which are not fed with fluid will be effected, compensating for the small variations in volume of this enclosed system during the rotation of the cylinder block.

The invention will, however, be better understood and various other characteristics as well as their advantages will be apparent from the following description of embodiments, given by way of example, with reference to the accompanying drawings in which:

FIGURE 1 is an axial section of an hydraulic motor utilizing the method and arrangement in accordance with the invention,

FIGURE 2 is a section on the line IIII in FIGURE 1,

FIGURE 3 is a diagram of a variant of the control for taking the cylinders out of circuit,

FIGURE 4 is a partial view corresponding to FIGURE 1, showing a variant of the enclosed system connecting the cylinders out of circuit.

Referring to these drawings, the hydraulic motor comprises a cylinder block 1 supported on a driving shaft 2 rotatably mounted in a casing 3. Radial cylinders 4 (only two are shown in the figure) are disposed in the block 1, within which operate pistons 5 carrying rollers 6 at their outer ends displaceable by cams 7 fixed to the casing 3.

Hydraulic fluid for controlling the movement of the pistons is supplied from a reservoir 9 at atmospheric pressure by a pump 8. A known type of reversing valve is provided in the delivery pipe 11 of the pump. This delivery pipe is connected to the inlet pipe 12 of the distributor 13 of the motor, this distributor in the example shown comprising two elements 13a and 13b fixed to one another by means not shown and fixed also to the casing. An annular chamber 14 is disposed between the two elements 13a and 13b of the distributor, communicating on one side with the inlet pipe 12, and on the other side with a number of inlet ports 16 leading to the external surface of the element 13a of the distributor, by means of conduits 15. The inlet ports 16 are equally spaced circumferentially and are equal in number to the number of undulations of the cams 7. Supply ports 17 corresponding to each cylinder 4 situated in the same transverse plane as the ports 16, are provided in the cylinder block. These supply ports, lead into a first chamber 18 communicating by means of a conduit 19 substantially parallel to the axis of the cylinder block, with a second chamber 20 in which is provided a port 21 in communication with the corresponding cylinder 4. Evacuation of the fluid from the cylinders, is effected through outlet ports 22, corresponding to the inlet ports 16, interpolated with the latter, and disposed in the same transverse plane. These outlet ports lead into an axial chamber 23 disposed between the two elements 13a and 13b and communicating through an outlet pipe 24 with a pipe 25 returning to the reservoir 9. The normal operation of such a motor is well known and will not, therefore, be described in detail. In particular it is known that the sense of rotation of the motor can be changed by operating a reversing valve 10, the members referred to as inlets then becoming outlets and vice versa.

However, if certain cylinders 4 corresponding to those shown at the bottom of FIGURE 1, are permanently fed with working fluid, the supply conduit 17 to 21 of certain others may be closed, which enables the operating characteristics of the motor to be modified.

Thus, it will be noted that the closing arrangement of the circuit is in accordance with the way in which the method of the invention can be carried into effect.

For this purpose, a slide-valve 26 is slidably mounted parallel to the axis of the cylinderblock in a bore 27 corresponding to each cylinder 4 which is to be taken out of circuit. The slide valve comprises essentially a central piston 28 of the same diameter of the bore 27 and of the conduit 19 which is thus capable of being closed. On opposite sides of the piston 28, are provided two pistons 29 and 30 equal in diameter to piston 28, and fixed also on the slide valve 26.

In the embodiment shown in FIGURE 1, the piston 29 has longitudinal grooves 29a and for this reason does not present. any resistance to its displacement under the conditions to be explained hereinafter. A spring 31 is supported by the piston 30 and tends to bias it towards the right in the figure into the position where conduit 19 is open. A screw plug 32 provides for abutment for the spring 31 and is provided with an axial bore 32a, thus putting the left-hand face of the piston 3t) in communication with the pressure in casing 3, that is to say practically atmospheric pressure. An annular passage 33 provides communication between the bores 27 normally closed by the pistons 28, and the internal surface of the cylinder block 1.

A pipe line 35 is provided in the distributor 13, the opening 34 of which at the outer surface of the distributor, is situated opposite the annular passage 33.

In one example (FIGURE 1) the pipe line 35 can be connected, either to the return pipe line 25 or the reservoir 9 by a pipe line 38, by means of a two-way slide valve 36. It is to be noted that in this case, the pipe line 35 is provided with a check-valve 37 calibrated at a low pressure having regard to the pressure of the working fluid, for example, a pressure of the order of 0.5% to of the pressure of the working fluid.

In the second example (FIGURE 3), the pipe line 35 can be connected to a pressure accumulator 39 by the valve 36 already described, the accumulator 39 being fed by any known means (not shown).

In the embodiment shown in FIGURE 4, the piston 29 is not provided with longitudinal grooves (as in FIGURE 1) and the chamber 27a of the bore 27 communicates with a radial passage 33a which is itself situated at the end opposite of the opening 34 (in FIGURE 1) and communicates with pipe line 35. The passage 33 is closed by the external periphery of the element 13a of the distributor and communicates only with the central part 27b of the bores 27.

Thus, the operation of the device for taking certain cylinders out of circuit is as follows:

The various members being in the positions shown in full lines in the drawing, the valve 36 is positioned so as to establish communication between the pipe line 35 and the pipe line (FIGURE 1) or the accumulator 39 (FIGURE 3). The fluid under pressure (back-pressure created by the calibrated check valve 37 or pressure of the accumulator) transmitted to the bores 27 (FIGURE 1) or the chambers 27a (FIGURE 4) through the pipe line and the annular passage 33 or 33a pushes the pistons 28 of the slide valves 26 against the action of the springs 31. This movement of the pistons 28 closes the feed conduits 19 of the corresponding cylinders 4, thus isolating these cylinders from the working fluid circuit, and open the communication between the feed chambers 20 of the cylinders and the corresponding bores 27 (or 271)). Thus, all the cylinders 4 which are not to be fed, are connected hydraulically by the annular passage 33, the enclosed system consisting of the cylinder assembly, the passage 33, and eventually the pipe line 35 (FIGURE 1), being independent of the working fluid circuit.

In the case. of the variants of FIGURES 3 and 4, it can even be said that the enclosed system is completely fluid tight, although possibly of variable volume (FIGURE 3).

When the reversing valve 10 is operated up, or down, the motor is caused to rotate in one direction or the other. The piston 5 of certain of the cylinders 4 outside the circuit will be forced downwards and consequently will compress fluid in the enclosed system referred to, this fluid tending to repel the pistons in the other cylinders outside the circuit in such a way that all the rollers 6 will be maintained in contact witht he .cams 7. Thus, a completely silent operation of the motor is obtained even at high speed. Nevertheless, as indicated above, it may be that the volume of fluid compressed by certain pistons does not compensate exactly for the volume capable of being introduced in theo ther cylinders, for all positions of the cylinder block. Thus, at this stage the aforesaid stufling operation (i.e. replenishing and partial draining) is brought into operation, that is to say the possibility of introducing and then removing, a quantity of compensating fluid (FIGURES 1 and 3 only). The pressure accumulator 39, is capable of supplying this stuffing because of its expansible fluid chamber.

Likewise, in the first example (FIGURE 1) the back pressure created in the return working fluid circuit by the calculated check-valve 37 enables a fluid reserve to be disposed of or a fluid surplus to be absorbed at the inlet to the valve 36.

If it is desired to change speed, it is suflicient to operate the valve 36 so as to establish direct communication between the pipe line 35 and the reservoir 9. The springs 31 biases the slide valves 26, and the pistons 28 are displaced, on opening of the supply pipe lines 19 of the cylinders 4, previously taken out of circuit. The cylinder volume of the motor is thus increased and, with a constant delivery of fluid, the rotary speed decreases, It could however, be restored to its initial value by a simple operation of the valve 36 to establish communication between the pipe line 35 and either the pipe line 25 or the accumulator 39.

It will of course be understood, that the invention is not limited to the embodiments just described but extends, on the contrary, to all variants. In fact, it can be carried into eflect in different ways according to the particular characteristics of the motors to which itis applied. Also, as indicated (FIGURE 4) the control for taking certain cylinders out of circuit, can be separated from the assembly of pipe lines defining the enclosed system with which all the cylinders outside the circuit cornmunit cate; the said enclosed system will thus be advantageaously, although not necessarily, of constant volume.

Finally, it will be evident that without departing from the scope of the invention, many groups of cylinders to be taken out of circuitseparately orv simultaneously may be provide each of these groups being associated with an enclosed system for subsequent connection to the same enclosed system.

I claim:

1. A hydraulic motor comprising, a rotary cylinder block, a plurality of radial cylinders in the block, pistons mounted for reciprocation in the cylinders, undulating cam means for supporting the pistons, a working fluid system including the cylinders, an auxiliary fluid system including selected ones of the cylinders, valve means to cut off the selected cylinders from the working system and connect them to the auxiliary system, and means at fording communication between the auxiliary fluid system and a source of fluid under relatively low pressure so that said selected cylinders pistons are continuously biassed against said undulating cam means by said source of fluid under relatively low pressure.

2. A hydraulic motor as claimed in claim 1 wherein the source of fluid under relatively low pressure is a pressure accumulator.

3. A hydraulic motor as claimed in claim 1 wherein the source of fluid under relatively low pressure is the working fluid system.

4. A hydraulic motor as claimed in claim 1 wherein the source of fluid under relatively low pressure is the fluid return side of the working fluid system and there is a calibrated check-valve arranged in the fluid return side of the working fluid system downstream of the point of communication with the auxiliary fluid system.

5. A hydraulic motor as claimed in claim 1 wherein the valve means are controlled by the fluid under relatively low pressure in communication with the auxiliary fluid system.

6. A hydraulic motor comprising, a rotary cylinder block, a plurality of radial cylinders in the block, pistons mounted for reciprocation in the cylinders, undulating cam means for supporting the pistons, a working fluid system including the cylinders to supply fluid under pressure to and return fluid from the cylinders, an auxiliary fluid system including selected ones of the cylinders, valve means to out off the selected cylinders from the working fluid system and connect them to the auxiliary system, and a control operable to establish communication between the auxiliary system and a source of fluid under relatively low pressure and to cause activation of the means to cut oif selected cylinders from the working fluid system so as to continuously bias said selected cylinders pistons against said undulating cam means.

7. A hydraulic motor as claimed in claim 6 wherein the source of fluid under relatively low pressure is a pressure accumulator.

8. A hydraulic motor as claimed in claim 6 wherein the source of fluid under relatively low pressure is the working fluid system.

9. A hydraulic motor as claimed in claim 6 wherein the source of fluid under relatively low pressure is the return side of the working fluid system and there is a calibrated check-valve arranged in said return side downstream of the point of communication with the auxiliary fluid system.

10. A hydraulic motor as claimed in claim 6 wherein the valve means are located in said cylinder block and are rotatable therewith.

References Cited UNITED STATES PATENTS 5/1939 Alpern 9l204 5/1960 Wadefelt 91-205 PAUL E. MASLOUSKY, Examiner. 

